determining an aircraft drag polar. - another rv-10 · pdf filea drag polar is a graph of an...
TRANSCRIPT
Mike Andresen
What is it?◦ A drag polar is a graph of an aircraft drag versus indicated air
speed.What good is it?◦ Many performance parameters can be determined from the
drag polar. Best Climb, Glide ratio, optimum cruise, etc.What is it for my airplane?◦ This presentation is to give you a procedure to measure it.
Conduct flight test.◦ Level flight, various airspeeds and flap configurations.◦ Record density altitude of flight test.◦ Record engine MP/RPM for power determination◦ Note aircraft weightPlot Data◦ Determine engine power from settings◦ Convert power to thrustDetermine Aircraft Performance Parameters
Flaps 0IAS TAS MP RPM SL Pwr MP RPM SL Pwr
60 64.265 69.6 15 1900 6670 74.9 15.5 2050 7875 80.3 15.5 2100 8280 85.6 15.5 2150 8485 91 15 2200 82 15.5 2200 8690 96.3 16 2200 92 16 2200 9295 102 16.5 2200 98 17 2200 102
100 107 18 2200 112 18 2200 114105 112 18 2300 120 19 2200 122110 118 20 2300 132 20 2200 132115 123 22 2300 158 21.5 2200 146120 128 23 2300 168 22 2250 154125 134 25 2300 188 24 2300 178130 139 25 2300 188
Test 1 Test 2
Thrust = 325 * Power / True AirspeedFlaps 0IAS TAS MP RPM SL Pwr MP RPM SL Pwr MP RPM SL Pwr avg Thrust
60 64.265 69.6 15 1900 66 15 1850 64 65 30470 74.9 15.5 2050 78 15 1900 66 72 31275 80.3 15.5 2100 82 15 2000 72 77 31280 85.6 15.5 2150 84 15 2100 75 80 30285 91 15 2200 82 15.5 2200 86 15 2200 82 83 29890 96.3 16 2200 92 16 2200 92 16 2200 92 92 31095 102 16.5 2200 98 17 2200 102 17 2200 102 101 322
100 107 18 2200 112 18 2200 114 18 2200 114 113 344105 112 18 2300 120 19 2200 122 19 2200 122 121 351110 118 20 2300 132 20 2200 132 132 364115 123 22 2300 158 21.5 2200 146 152 401120 128 23 2300 168 22 2250 154 161 408125 134 25 2300 188 24 2300 178 183 445130 139 25 2300 188 188 439
Test 3Test 1 Test 2
250
300
350
400
450
500
60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
IAS (kts)
Thrust (Drag) (lbs)for level flight
0 flap
10 flap
20
40
Low end of curve dominated by induced drag◦ Proportional to 1/V2
High end dominated by parasitic drag◦ Proportional to V2
Drag = a/V2 + b V2
b = a Vgl-4 where Vgl = best glide.
250
300
350
400
450
500
64 70 75 80 86 91 96 102 107 112 118 123 128 134 139
60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 IAS
TAS
250
300
350
400
450
500
64 70 75 80 86 91 96 102 107 112 118 123 128 134 139
60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
0 deg
10 deg
20 deg
40 deg
Drag(lbs)
IASTAS
250
300
350
400
450
500
64 70 75 80 86 91 96 102 107 112 118 123 128 134 139
60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
0 deg
10 deg
20 deg
40 deg
Drag(lbs)
IAS
TAS
2300 lbs
L/D = 2300/300 = 7.7
L/D = 5.4
Small initial deflections cause noticeable changes in CLwithout large changes in CD. In General:◦ First 50% of flap deflection causes >50% total change in CL◦ Last 50% of flap deflection causes >50% total change in CD
250
300
350
400
450
500
64 70 75 80 86 91 96 102 107 112 118 123 128 134 139
60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
0 deg
10 deg
20 deg
40 deg
Drag(lbs)
Best Glide = 80 kts IAS
IAS
TAS
250
300
350
400
450
500
64 70 75 80 86 91 96 102 107 112 118 123 128 134 139
60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
0 deg
10 deg
20 deg
40 deg
Maximum endurance (max time airborne)◦ Vme = Vgl / 1.316◦ = 80 / 1.316 = 61 kts
Drag(lbs)
Max Endurance = 61 kts IAS
IASTAS
Optimum Cruise◦ Best fuel flow per knot◦ Voc = Vgl * 1.316◦ = 80 * 1.316 = 105 kts
Fly around taking some dataDo some data analysisDetermine Glide Ratio, Best Glide Speed, Vx, Vy, Optimum Cruise and Max Endurance Speed.